6.8-stable review patch. If anyone has any objections, please let me know.
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From: Beau Belgrave beaub@linux.microsoft.com
[ Upstream commit bd125a084091396f3e796bb3dc009940d9771811 ]
When the ABI was updated to prevent same name w/different args, it missed an important corner case when fields don't end with a space. Typically, space is used for fields to help separate them, like "u8 field1; u8 field2". If no spaces are used, like "u8 field1;u8 field2", then the parsing works for the first time. However, the match check fails on a subsequent register, leading to confusion.
This is because the match check uses argv_split() and assumes that all fields will be split upon the space. When spaces are used, we get back { "u8", "field1;" }, without spaces we get back { "u8", "field1;u8" }. This causes a mismatch, and the user program gets back -EADDRINUSE.
Add a method to detect this case before calling argv_split(). If found force a space after the field separator character ';'. This ensures all cases work properly for matching.
With this fix, the following are all treated as matching: u8 field1;u8 field2 u8 field1; u8 field2 u8 field1;\tu8 field2 u8 field1;\nu8 field2
Link: https://lore.kernel.org/linux-trace-kernel/20240423162338.292-2-beaub@linux....
Fixes: ba470eebc2f6 ("tracing/user_events: Prevent same name but different args event") Signed-off-by: Beau Belgrave beaub@linux.microsoft.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace_events_user.c | 76 +++++++++++++++++++++++++++++++- 1 file changed, 75 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index fce5ed5fec50f..704de62f7ae16 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -1923,6 +1923,80 @@ static int user_event_trace_register(struct user_event *user) return ret; }
+/* + * Counts how many ';' without a trailing space are in the args. + */ +static int count_semis_no_space(char *args) +{ + int count = 0; + + while ((args = strchr(args, ';'))) { + args++; + + if (!isspace(*args)) + count++; + } + + return count; +} + +/* + * Copies the arguments while ensuring all ';' have a trailing space. + */ +static char *insert_space_after_semis(char *args, int count) +{ + char *fixed, *pos; + int len; + + len = strlen(args) + count; + fixed = kmalloc(len + 1, GFP_KERNEL); + + if (!fixed) + return NULL; + + pos = fixed; + + /* Insert a space after ';' if there is no trailing space. */ + while (*args) { + *pos = *args++; + + if (*pos++ == ';' && !isspace(*args)) + *pos++ = ' '; + } + + *pos = '\0'; + + return fixed; +} + +static char **user_event_argv_split(char *args, int *argc) +{ + char **split; + char *fixed; + int count; + + /* Count how many ';' without a trailing space */ + count = count_semis_no_space(args); + + /* No fixup is required */ + if (!count) + return argv_split(GFP_KERNEL, args, argc); + + /* We must fixup 'field;field' to 'field; field' */ + fixed = insert_space_after_semis(args, count); + + if (!fixed) + return NULL; + + /* We do a normal split afterwards */ + split = argv_split(GFP_KERNEL, fixed, argc); + + /* We can free since argv_split makes a copy */ + kfree(fixed); + + return split; +} + /* * Parses the event name, arguments and flags then registers if successful. * The name buffer lifetime is owned by this method for success cases only. @@ -1946,7 +2020,7 @@ static int user_event_parse(struct user_event_group *group, char *name, return -EPERM;
if (args) { - argv = argv_split(GFP_KERNEL, args, &argc); + argv = user_event_argv_split(args, &argc);
if (!argv) return -ENOMEM;